1. Field of the Invention
The present invention relates to a hand operated braking system for a hand cart. More particularly, the present invention includes a hand cart braking system with a single clutch braking system.
2. Summary of Related Art
Hand carts are well known in the material handling industry for loading and unloading material from trucks and trailers. Hands carts are used not only at truck loading docks, but also at retail establishments and other delivery points. Hand carts are also essential devices for moving loads within warehouses and production facilities. The primary construction of a hand cart includes two wheels on a single axle, two vertical frame members with cross frame members, a handle at the top of the frame, and a load engaging flange plate at the bottom of the frame. A typical braking system for a hand cart is a hand operated system positioned on the handle at the top of the frame.
A significant problem which occurs during use of a hand cart is controlling a loaded hand cart on an inclined surface. Inclined surfaces are encountered quite frequently in many hand cart applications, such as maneuvering hand carts up and down truck unloading ramps. The inability to control a loaded hand cart on an inclined surface frequently results in damage to the load being moved and injury to the person operating the hand cart.
When using a hand cart, the operator will frequently use only one hand to control the cart and the other hand is used to engage and steady the load being carried on the cart. Since the operator utilizes one hand on the load, the braking systems on hand carts are generally positioned at the handle and designed for one hand operation.
One of the problems with braking systems on hand carts is that the braking force should be applied uniformly to the two wheels. When the braking force is applied unevenly, the hand cart will not roll in a straight path and will swing to one side. When an operator is applying the brake while rolling a loaded hand cart down a loading ramp, uniform braking to facilitate straight path operation is essential.
Another requirement for hand cart operation is maneuverability. Since hand carts must be operable on a non-linear path when moving a load, it is essential that the braking system not adversely effect the maneuverability of the hand cart. Independent operation of the wheels is required to permit the hand cart to turn corners in a controlled manner.
A majority of hand carts do not have any braking capabilities and the person using the hand cart must use their own strength to stop and/or control a cart on an inclined surface. Several braking systems for hand carts are disclosed in the prior art. The hand carts of the prior art typically include independent wheels and a fixed axle which are mounted on a bracket or other mounting means on the lower corners of the frame. A separate braking mechanism is required for each of the wheels. One of the problems with the prior art systems has been achieving uniform braking force at the two wheels.
In the prior art, Honeyman (U.S. Pat. No. 3,276,550) discloses an U-shaped brake rod mounted between the two wheels. Projecting ends are positioned above the wheels to form a braking means. When the handle is pulled, the projecting ends are positioned in front of the wheels such that a braking force is applied to limit the rotation of the wheels. The forward movement of the wheels tends to cause greater engagement between the wheels and the projecting ends which creates a self actuating feature.
In attempting to improve the maneuverability of the hand cart during braking, Malloy (U.S. Pat. No. 3,486,587) discloses the benefits of having independent operation of the brakes with a single operating handle. A special linkage is attached to the brake shoes of the wheels to provide independent braking.
Wetzel (U.S. Pat. No. 3,368,974) discloses wheels mounted by separate bearings mounted on a fixed axle to provide for independent rotation. A hydraulic system is used to actuate a caliper-type disc brake system mounted at each of the wheels. Equal braking force is applied to each of the wheels. Boyd (U.S. Pat. No. 4,142,732) teaches a disc braking system to brake the main axle shown in the specialized hand cart. The wheels are independently mounted on star-shaped plates, and the plates rotate when the cart is used on stairs. The hand brake system locks the main axle to prevent the plates from rotating.
Laird (U.S. Pat. No. 4,819,767) discloses a braking system which can be used on both two-wheel and four-wheel hand carts. Brake discs are mounted in the frame and are selectively extended from the frame to engage the sidewalls of the wheels to prevent rotation of the wheels.
A hand cart having a brake drum mounted about the hub of the wheels is disclosed in Hedrick (U.S. Pat. No. 5,390,943). The wheels operate independently. The brakes are operated by a single handle with two separate brake actuating cables to two independent brakes. The stopping force to each wheel is equalized by a brake adjusting screw on each brake.
Hlebakos (U.S. Pat. No. 5,433,464) shows a braking system having wheels with a braking shoe and backing plate assembly. A pulley system and cam followers are used to provide equal braking pressure to each of the wheels. Such a braking system is intended for retrofitting on existing hand carts.
The braking system disclosed in Grieg (U.S. Pat. No. 5,524,731) teaches a brake bar mounted on the cart and extending between the two wheels of the cart. Brake pads are mounted on the brake bar which engage the wheels. A step plate is attached to the bar to permit the operator to tilt the hand cart into an operating position.
Wyse (U.S. Pat. No. 5,722,515) discloses a hand cart braking system having a rotatable split axle mounted laterally between the wheels of the hand cart. The axle is split in the middle of the axle to form two distinct segments. Each axle segment rotates with its respective wheel, and the axle segment and wheel on one side of the cart rotate independently of the other axle segment and wheel combination. A brake is mounted on the axle at the junction of the two axle segments. An actuator handle is mounted on the cart at a convenient point for actuating the brake. When the brake is manually operated, the braking force is applied to both segments of the axle to smoothly stop the hand cart. The brake is preferably a disc brake or a drum brake, although other braking devices may also be used in the present system. The brake utilizes a double clutch system to engage and disengage the brake.